1. Technical Field of the Invention
The present invention relates generally to semiconductor devices and, more particularly, to a concentrated photovoltaic (CPV) receiver module or solar cell assembly which includes a molded, cast or machined hollow funnel having a highly reflective internal surface for use in guiding focused solar rays to the receiver die surface of the receiver die of the module or assembly.
2. Description of the Related Art
Photovoltaic cells are a well known means for producing electrical current from electromagnetic radiation. Traditional photovoltaic cells comprise junction diodes fabricated from appropriately doped semiconductor materials. Such devices are typically fabricated as thin, flat wafers with the junction formed parallel to and near one of the flat surfaces. Photovoltaic cells are intended to be illuminated through their so-called “front” surface. Electromagnetic radiation absorbed by the semiconductor produces electron-hole pairs in the semiconductor. These electron-hole pairs may be separated by the electric field of the junction, thereby producing a photocurrent. Currently known photovoltaic cells typically have a generally quadrangular (e.g., square) configuration defining four peripheral side edges, and include a pair of bus bars which are disposed on the top or front surface and extend along respective ones of an opposed pair of the side edges. The bus bars are used to facilitate the electrical connection of the photovoltaic cell to another structure, as described in more detail below.
There is currently known in the electrical arts semiconductor devices known as CPV receiver die packages or modules. Currently known CPV modules typically comprise a ceramic substrate having a conductive pattern disposed on one side or face thereof. Attached to the substrate and electrically connected to the conductive pattern are electrical components, including a pair of preformed wire connectors and a packaged diode. Also attached to the substrate and electrically connected to the conductive pattern thereof is a CPV receiver cell or die. The electrical connection between the receiver die and the conductive pattern is often facilitated by a pair of punched thin metal foil or braided ribbon/mesh connectors which extend along and are welded or soldered to respective ones of opposed sides of the receiver die, which typically has a quadrangular or square configuration as indicated above. More particularly, the pair of punched thin metal foils or braided ribbon/mesh connectors are welded or soldered to respective ones of the bus bars on the top or front surface of the receiver die. In certain existing CPV modules, the electrical connection of the receiver die to the conductive pattern is facilitated by the use of multiple wires bonded to the bus bars on the front surface of the receiver die and the bond pads of the conductive pattern of the substrate, the wires being used as an alternative to the aforementioned braided ribbon or mesh interconnects. When wires are used as an alternative to the ribbon/mesh type interconnects, such wires require encapsulation, over-molding or other protection from the environment for long-term reliability of the CPV module including the same.
The CPV module may further include a light concentration means or optical light guide which is adapted to concentrate solar radiation onto the front surface of the receiver die. In this regard, CPV modules typically include a polished glass prism which is operatively connected to the solar cell or receiver die, and is used to guide the focused solar rays to the front surface of the receiver die. The prism also prevents light leak or mis-focused solar energy that may otherwise cause damage to the structures around the receiver die.
However, a drawback in the design of current CPV modules is that the aforementioned prisms require a special optical adhesive to attach the bottom surface thereof to the receiver die. The attachment of the prism to the receiver die also presents a myriad of problems in relation to the assembly of the CPV module. These problems include difficulties in automating the pick-up and placement of the prism, the susceptibility of the prism to cracking, chipping, or other contamination, the susceptibility of trapped air bubbles being present in the optical adhesive used to attach the prism to the receiver die, the delamination of the optical adhesive during transport or use of the CPV module, light loss through interface reflection or internal absorption, and optical adhesive “creep” on the sides of the prism that causes light coupling loss. In addition, the natural shape of a focus spot from currently known concentrating optics (e.g., prisms) is circular, whereas the front surface of the receiver die is normally square, thus creating a mismatch in geometry. Typically, such mismatch is accommodated by either truncating the focus spot on the entering surface of the prism which has the detrimental effect of introducing additional light loss, or oversizing the prism which has the detrimental effect of adding weight and cost. Still further, currently known glass prisms are heavy in weight and expensive to manufacture.
The present invention addresses these and other shortcomings of prior art CPV modules by using a molded, cast or machined funnel fabricated from a highly reflective material or plated with a reflective film to guide focused solar rays onto the front surface of the receiver die or cell of a CPV module. These, and other features of the present invention will be described in more detail below.
Common reference numerals are used throughout the drawings and detailed description to indicate like elements.